Optical components provide and can provide many different functions in large scale integrated circuitry. Optical back planes are used to connect several circuit boards to each other. Such back planes require optical modems to communicate between the back plane and the chips on the circuit card. Optical communication between chips on a single card is under development, as is optical communications using optic fiber for networking, internet and other communications. It has also been proposed to provide optical input/output ports on microprocessors to allow for testing and other functions. The optical interface circuitry required to support these applications may be used only infrequently and may involve high power consumption components such as analog amplifiers, sample and hold capacitors etc. Accordingly, it is preferred that the circuitry necessary to support the optical communications only be powered when the circuitry is in use. This saves power and reduces heat, which is particularly desirable in a large scale integrated circuit environment.